Are things moving towards a political crisis at the heart of the coalition – a crisis big enough to trigger its early collapse and thus a general election this year? If so, is David Cameron delighted at the prospect? These are the questions just starting to be raised at Westminster. And however startling they seem, they make a kind of sense.

All the polling now points to a May defeat for the AV campaign and a slaughter of Liberal Democrat councillors. No to voting reform; no to Nick Clegg. This will be accompanied by a headline revival in Labour's fortunes which, I cautiously suggest, may not matter very much.

Clegg's ferocious outburst against Cameron at the weekend, talking about his hopes for "the death rattle" of the nasty, lying, mendacious rightwing clique that his ex-best friend, the prime minister, heads, was extraordinary. To show it wasn't just a heat of the moment display of frustration, Chris Huhne and Simon Hughes piled in, accusing a range of Tories, from George Osborne to Baroness Warsi, of being liars.

You could decide that all of this is mere synthetic indignation, designed to pump up the pro-AV vote and boost Lib Dem identity ahead of the local elections next week. Do Clegg and Cameron grin in private and shrug their shoulders about the show they have to put on? Is it all just for show?

It isn't – this breakdown in friendly relations is real. Why? Because Clegg and his colleagues have lost a catastrophic amount of authority, while Cameron and his Tory friends are on a roll. The dynamics have changed. The old Cameron would have been bending over backwards to appease and soothe Lib Dem upset. The new Cameron doesn't seem to give a fig.

Perhaps the best example isn't the AV vote itself, where the "pro" camp accuse the antis of smears over the cost of the new system, but the apparently more minor row over internships. Clegg's attack on Cameron's rather lordly insouciance about favours for friends, and friends' children, is significant. As I have argued before, about the only thing the Lib Dems could take away from the coalition, claim to have fought for, and get real electoral support from, is their fairness agenda. Whether it's tax credits or positive discrimination for state school pupils at university, this is the thing that most obviously sets them apart from Tory instincts.

Clegg's decision to seize on the chaps' network of internships plays directly to this question of fairness. Clegg was picking a fight. But what's more interesting is Cameron's response. It takes two to tangle. He could have mumbled something conciliatory, but he went the other way.

He doesn't sound any longer like a prime minister desperate to patch over differences and jolly things along. Vince Cable, who sounds like a man jumping on the plank before he dives overboard, is getting no comfort from Tory colleagues over immigration. He lost over Murdoch. If the Lib Dems lose AV, they will find they have almost nothing left. The fairness agenda will come down to university access, with Tory ministers determined to block real change.

The truth is, Cameron is now so clearly in control that the hinge on which the whole coalition used to depend – his cordial relationship with Clegg – matters much less. Cameron has undoubtedly grown into the job. Privately, his political enemies are almost unanimous in admitting that he is showing a sureness of touch and a self-confidence they didn't expect.

Electoral reform campaigners have noticed that every time Clegg speaks for them, their ratings fall, while every time Cameron speaks against, the no campaign's ratings rise (please Nick, pipe down for the next 10 days).

So whereas six months ago it looked obvious that Cameron's best interests lay in holding the coalition together for the course of a full parliament, then going to the country on the back of a year or two of economic recovery and tax cuts, that's no longer so clear. Ed Miliband's Labour is only just beginning the process of rebuilding and rethinking. The grieving isn't over. Money is tight. (Unlike the Tories, who have already built up a new war chest.)

These coming local elections will show a Labour revival. There will be back-slapping and some good headlines for Labour, though not in Scotland. But none of this will tell us much about the possible outcome of a general election – too few people voting for a start. Nor are the current national opinion polls much of a guide, since people have not turned their minds to a possible election.

But if I were a Tory strategist, I would feel the party's underlying level of support was surprisingly strong. I would look at the fact that Labour is still in the early stages of recovery and that the Lib Dems are coming apart at the seams. I would recall the hard decisions still ahead, with a major bust-up over European budgets likely; and I would remember how quickly foreign interventions, such as the Libyan one, can go wrong. I would note the Lib Dem enthusiasms were riling my own supporters and I would think … "hmm, very interesting". I would also think my decisiveness in going for a snap election would contrast nicely with my predecessor, Gordon Brown, who famously flinched from an election in autumn 2007.

Of course, it's one thing to realise that an early election could well produce a Tory victory with a decent majority. It's another to successfully engineer it. The public don't like unnecessary elections, so the coalition would have to fall apart so clearly and decisively that an election became inevitable. How could that come about? Cameron calling in Cable and sacking him, without more than a cursory call first to Clegg? A stonking row over Lansley's NHS plans? Or university access?

The break could be accomplished in any number of ways, and all the cards are with Cameron. The Lib Dems are simply trapped. They will get few, if any, meaningful concessions. The longer they stay in the coalition, the weaker they will be. But if they bring it down and cause an election, they will be hammered.

An election sooner rather than later now looks like a good option for the Conservatives, and as this realisation spreads through the party, there will be an increasingly tough, even brutal, attitude to their junior partners. Lib Dems' anger about the Tories is not feigned – you can hear it, feel it, taste it and touch it. They seem at breaking point. From now on, however, Cameron is more likely to let them break than to help them out. That's why an election this year is no longer impossible – speculation, but no longer wild speculation.